This invention relates to electronically assisted stethoscopes, and more particularly to electronic conversion units for converting a conventional stethoscope into a phonostethoscope whose authenticity of sound amplification and ease of operation are within range of those directly and indirectly involved with the medical field.
It is common procedure during the work up of a patient to include electrocardiogram recordings in the patient's chart. Such a recording provides evidence of important cardiac functions; rate, rhythm, axis hypertrophy, and miscellaneous drugs effects. Unfortunately the attempt to solve problems of cardiac defects, valvular hemodynamics, and other physiological abnormalities are often limited by the individuals acoustic capacity and memory. Specialized equipment is available to aid this aural registering, including a variety of electronic recording and analysis devices. However these devices are often expensive, non-mobile and require the services of trained personnel.
Conventional stethoscopes often employ a resonant peak within their frequency response characteristics, this peak often falling nominally between 50 Hz and 200 Hz. Certain stethoscope models exhibit peaks in their response at 1500 Hz to 3000 Hz. These characteristics are determined by a number of factors. Among the major contributors to resonant peaks are chestpiece chamber volume and diaphragm thickness/mass ratio. These resonant peaks are often highly useful in that they are utilized by physicians to accentuate certain commonly encountered sounds.
Electronic stethoscopes have been available for many years but they have not gained wide acceptance by medical practitioners because of their inconveniences in use, their high cost, high weight and bulk, difficulty in attachment, and often lack of easy mobility. Additionally, and perhaps more importantly, the electronic stethoscopes previously available have imposed a burden on the user in the form of a highly unnatural sounding instrument, or at best, an instrument to which the user has not been attuned. Representative prior art includes Slosberg et al U.S. Pat. Nos. 3,846,585, Keesee 3,539,724, Minsky 2,385,221, Cefaly et al 3,247,324, Clark et al 3,182,129, Croslin 3,233,041, and Andries et al 3,160,708, each of which fails to recognize the importance of providing a light weight transducer assembly easily mountable and located at the earpiece locations which is the terminal point of exit of the sound from the air column.
The prior art devices may be viewed as utilizing techniques of basically three general types. The first type utilizes an electronic input sensor and amplification device at the chestpiece location, and thereafter employs purely passive acoustic means throughout the length of the vibrating air column and into the earpieces. A second type utilizes a combined electronic input sensor and amplification means at some intermediate point in the vibrating air column; while the input sensor and the output means are of conventional acoustic configurations. The third type utilizes electronic amplification techniques at both the chestpiece and at some intermediate point within the vibrating air column, while the earpieces remain conventional.
I have discovered that the location of the amplification and frequency controls in the prior art devices has not resulted in optimal positioning of the devices and in turn have often created additional problems.
Considering the stethoscope and the human body as an integral unit for transmission of sounds, it becomes apparent that whatever form of amplification, or frequency response shaping that interrupts the sound flow along its route from origin to exit of the stethoscope, it will invariably cause alterations in sound characteristics. More importantly, it often alters the character of the perceived sound as the physician has been trained to recognize it. To alleviate this situation, this invention utilizes the concept of placing the amplifier unit and frequency response shaping elements at the final exit of the sound from the stethoscope (i.e., earpieces) resulting in substantially unaltered sound flow, and a highly natural sounding electronically assisted stethoscope.
It will become obvious that this new combination and configuration has advantages over existing electronically aided stethoscopes and may be of significant aid in diagnostic and teaching situations when utilized in conjunction with a specific recording format and presently existing medical procedures.